In the context of future air operations such as high level navigation performance operations on the approach and on take-off, of the RNP SAAAR (“Required Navigation Performance with Special Aircraft and Aircrew Approval Required”) type or of the RNP AR (“Required Navigation Performance with Authorizations Required”) type, one of the problems to be solved is to make ever more secure the RNP type control system, in particular the guidance system.
Operations of the RNP type are operations carried out essentially with the aid of positioning sensors, particularly of the GPS (“Global Positioning System”) type, flight management computers of the FMS type and an automatic pilot means onboard the aircraft. Most flight management systems generate control instructions for guidance in the form of a roll command. This roll command is transmitted to the automatic pilot means whose task is to apply it. Such an embodiment is in particular provided on civil transport aircraft of the Airbus A320, A330, A340, and A380 type. The flight management systems are noncritical.
On civil transport aircraft there is no specific monitoring concerning the roll command originating from a flight management system. The flight management system is currently the largest contributor in the computation of failures of the “undetected loss of guidance” type. Furthermore, there is no specific monitoring linked to the small guidance loop input roll command. The guidance computer is therefore another significant contributor in the computation of failures of the “undetected guidance loss” type.
One of the problems posed by the aforementioned operations of the RNP SAAAR type is that they are based on the use of at least one flight management system. Currently, the operations of the RNP SAAAR type are similar to nonprecision approach operations and are therefore compatible with the use of a flight management system. However, a feature of operations of the RNP SAAAR type is that the aircraft must be guided along a precise flight path in space (referenced in the flight management system) to avoid potential obstacles (mountains, etc.) relatively closer than is currently achieved.
Also, even though, from a current regulatory point of view, the specific stability requirement is satisfied with the aforementioned usual architectures, it would be advantageous to be able to have an architecture that is significantly more robust against guidance failures, in the context of operations of the RNP SAAAR type. The future regulations could be based on such a more robust architecture.